Supplements that interfere with Warfarin

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Drug Interactions: Warfarin
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Trade Names : Coumadin



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·Vitamin K - Reduction of Action of Drug
·Coenzyme Q10 (CoQ10) - Possible Reduced Action of Drug
·Ginseng - Possible Reduced Action of Drug
·St. John's Wort - Possible Reduced Action of Drug
·Green Tea - Possible Reduced Action of Drug
·Vitamin C - Possible Reduced Action of Drug
·Vinpocetine - Possible Reduced Action of Drug
·Ipriflavone - Possible Increased Risk of Bleeding
·Garlic - Possible Increased Risk of Bleeding
·Ginkgo - Possible Increased Risk of Bleeding
·Devil's Claw - Possible Increased Risk of Bleeding
·Danshen - Possible Increased Risk of Bleeding
·Dong Quai - Possible Increased Risk of Bleeding
·Vitamin E - Possible Increased Risk of Bleeding
·Vitamin A - Possible Increased Risk of Bleeding
·White Willow - Possible Negative Interaction
·Other Herbs and Supplements - Possible Dangerous Interactions






Warfarin is an anticoagulant used to thin the blood and prevent it from clotting. It is a somewhat dangerous drug that can be affected by many substances, including foods. If you are taking warfarin, we don't recommend taking any herb or supplement except on a physician's advice.



Vitamin K
Reduction of Action of Drug Vitamin K is an antidote to warfarin and directly counteracts its effects. Do not take vitamin K while you are on warfarin.



Coenzyme Q10 (CoQ10)
Possible Reduced Action of Drug Coenzyme Q10 (CoQ10) is a substance somewhat similar in structure to vitamin K, and reportedly it, too, can reduce the effects of warfarin.1



Ginseng
Possible Reduced Action of Drug According to one case report, Asian ginseng (Panax ginseng) might decrease the effect of warfarin, preventing you from receiving its full benefit.2 For this reason, if you are taking warfarin, you should not use ginseng without consulting a physician.



St. John's Wort
Possible Reduced Action of Drug Evidence suggests that St. John's wort may interact with warfarin, possibly requiring an increased dosage to maintain the proper effect.3,4,5



Green Tea
Possible Reduced Action of Drug Because green tea contains vitamin K, drinking large amounts of it might reduce the effectiveness of warfarin.6



Vitamin C
Possible Reduced Action of Drug Vitamin C, when taken in high dosages (more than 1, 000 mg daily), has been reported to reduce the blood-thinning effect of warfarin.7–10



Vinpocetine
Possible Reduced Action of Drug Vinpocetine might impair the effectiveness of warfarin.11



Ipriflavone
Possible Increased Risk of Bleeding Warfarin causes increased risk of osteoporosis. You might think about taking the supplement ipriflavone while you use warfarin, because ipriflavone has been found to help prevent osteoporosis in certain circumstances. However, ipriflavone might raise warfarin levels in your body, which could cause a risk of bleeding.12 If you try this combination, you need to do so under physician supervision.



Garlic
Possible Increased Risk of Bleeding One of the possible side effects of the herb garlic is an increased tendency toward bleeding.13,14 According to two case reports, garlic might enhance the activity of warfarin, possibly amplifying the risk of bleeding problems.15



Ginkgo
Possible Increased Risk of Bleeding The herb ginkgo is known to reduce the ability of platelets (blood-clotting cells) to stick together and is suspected to increase the tendency toward bleeding.16,17 This leads to the natural concern that ginkgo might interact with warfarin, and there is one report of bleeding in an individual who had been taking both substances simultaneously.18



Devil's Claw
Possible Increased Risk of Bleeding According to one case report, the herb devil's claw might increase the potential for bleeding while taking warfarin.19



Danshen
Possible Increased Risk of Bleeding According to one case report, the Chinese herb Danshen (Salvia miltorrhiza) may increase the action of warfarin, which could potentially cause bleeding problems.20



Dong Quai
Possible Increased Risk of Bleeding According to one case report, dong quai may interact with warfarin, increasing the risk of bleeding.21



Vitamin E
Possible Increased Risk of Bleeding Vitamin E "thins" the blood, and on this basis it has been suggested not to combine it with warfarin. A 4-week study performed in 1996 found no additive effect.22 However, it is possible that problems might take longer than 4 weeks to develop, or that certain individuals might be more prone to an interaction.

The bottom line: Don’t risk serious bleeding problems. Avoid combining vitamin E with warfarin, except under the supervision of a physician.



Vitamin A
Possible Increased Risk of Bleeding Vitamin A might increase the effects of the blood thinner warfarin, which could potentially lead to an increased risk of bleeding.23



White Willow
Possible Negative Interaction The herb white willow contains substances very similar to aspirin. On this basis, it might not be advisable to combine white willow with warfarin.



Other Herbs and Supplements
Possible Dangerous Interactions Based on their known effects or the effects of their constituents, the herbs and supplements aortic glycosaminoglycans, bioflavonoids (of various types), chamomile, Coleus forskohlii, feverfew, fish oil, ginger, horse chestnut, OPCs (oligomeric proanthocyanidins), papaya, phosphatidylserine, red clover, and reishi might not be safe to combine with warfarin, but this has not been proven.





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1. Spigset O. Reduced effect of warfarin caused by ubidecarenone [letter]. Lancet 344(8933): 1372–

Oh dear Pam

Lists of very necessary food based supplements that interfere with coumadin. As per your great cut and paste post about coumadin it really does make you wonder if anyone wants anyone to get well.

I worry that some people may take lists like these too seriously and deny their body much needed nutrients.

Fran

Fran:

I agree with you and did post it more for the information value. I think that knowing what things might be altering our PT/INR outcomes would be valuable information. I don't think the reference refers to these substances in their natural form either, but rather supplements. I do take vitamin C when I feel a cold coming on, and I always take vitamin E. I take it for fibrocystic breasts and the extreme tenderness that accompanies that. It's the only thing I have found that works. However I do want to be aware of what interferes, so that if I do decide to take something, I will take it very regularly so that my Coumadin dose can be adjusted around it, just like I do for green leafies.


Pam

Pam

I think you have hit the nail on the head.

When on Coumadin, you must keep your intake of these thinks consistent and if you start taking them, coordinate it with whoever is monitoring your INR.

Its not that you must avoid these things, you must take them consistently. A lot of people seem to think that you should not consume them at all. I guess that is one way to achieve a consistent level.

Chris P